It is well known that heat and perspiration are normally generated around the toe area in shoes. This area tends to remain damp and is not easily ventilated because of the shoe construction. Therefore, after being worn for a period of time, the interior portion of the shoe will generate a bad smell and the moisture will attract and breed foot diseases. The situation will become more serious especially when wearing leisure type shoes and sneakers. Even if some holes are punched at the arch portion of the shoe, the situation is not improved very much. Nevertheless, there are some improved constructions of conventional shoes that have been designed to overcome the above mentioned drawbacks. Some of the improvements, however, are nothing more than the installation of an elastic pad in the upper portion of the shoe heel and building some ventilation channels in order to create an air circulation. This type of improvement is disclosed in U.S. Pat. Nos. 964,482 and 2,003,646. Other improvements include the installation of an air pump in the heel of the shoe or spaced apart resilient soles with air channels therebetween and orifices in the inner sole in communication with the air channels, such as disclosed in U.S. Pat. Nos. 2,441,879 and 4,468,869, respectively. Although the improved interior structures of these prior art shoes actually do have an effect of forcing ventilation of the shoe, the wearers have experienced certain drawbacks or the air pumping structure has certain deficiencies described hereinafter.
It is well known that a comfortable wearing of shoes generally demands a suitable enclosure of the foot, i.e. the foot can not have an excessive free space that permits movement. From the prior cited patents it is obvious that the elastic pad for pressing air out of the air cell is installed in the upper portion of the shoe heel and bulges out of its surface. In an attempt to get enough space for an air cell, it is necessary to have a large space for the elastic pad to move, or the ventilation effects will be greatly reduced. There is now a dilemma as to whether to have a comfortable fit or to have a greater compressible amount of air space. This means that when the wearer's foot is lifted from the ground, the depressing force on the elastic pad is eliminated and the pad is restored to its original position by the resiliency of the material of the pad. The elasticity for restoring the shape will make the wearer's heel move from the shoe heel for a certain distance and make the wearer have an uncomfortable feeling of a loose shoe. On the other hand, it is possible to solve the problem by permitting only a small movement between the wearer's heel and the shoe heel. This arrangement, however, will cause an insufficient compression space for the air cell.
There are also problems in those shoes that provide an air pump that is activated by the walking of the wearer. These problems usually manifest themselves over the life of the shoe. In some cases, the ventilation orifices and valves that form a part of the pumping apparatus, become clogged with debris, permit moisture to enter the pumping space, or become inoperative because of the valve construction. In addition, the prior art shoes generally require the outer or bottom sole to be of the same material, which is usually a molded material, as the heel. This construction greatly limits the design freedom of the shoes.